(a)[1]
The points plotted in Fig. 3.1 are not exactly on the best-fit line. Suggest a reason for this.
(b)[2]
Determine the gradient of the line in Fig. 3.1.
(c)[3]
The wire has a cross-sectional area of $0.12\,\text{mm}^2$. Use your answer in (b) to find the resistivity of the metal in the wire.
(d)[2]
The resistance $R$ of a set of wires is measured. Each wire is made of the same metal and has the same length, but the cross-sectional area $A$ is different for each one. On Fig. 3.2, sketch a graph to show how $R$ varies with $A$.